A data link protocol which provides all of the services mentioned in the previous slide is said to be connection-oriented. Such a protocol guarantees correct delivery of all data entrusted to it by higher-layer software. The data link protocols which are used in Wide Area Networks, where data rates are comparatively low and error probabilities are high, are usually connection-oriented. We discuss these protocols in this lecture.
Connectionless data link protocols simply transmit suitably addressed frames on the data link. They are commonly used in LANs. In this case, higher layer protocols take responsibility for error control.
INT32DC Data Communications